Discussion:
In Xp, USB audio devices capture or play with higher frequency than specified.
(too old to reply)
vinaykabadi
2009-09-16 21:47:38 UTC
Permalink
Hello,

I am an software engineer who works for audio development. I have used
Dsound for my capture playback, in the mean while I have found that
the USB camera with mic captures more than specified frequency. I
tried to capture at 8000Hz, 16 bits, mono. But when I get the average
results in 1 minutes.. I found that it is actually capturing around
8100 Hz. The same thing happens for playback too with USB Speakers.
Not only my code it seems that all the audio applications behave in a
same way.

But the sound card devices behaves properly i.e they capture more or
less 8000Hz. I dont understand why Xp behaves like this.

Can sombody help me out to get an work around to avoid this problem.

Regards
Vinay
Bob Masta
2009-09-17 12:09:21 UTC
Permalink
On Wed, 16 Sep 2009 14:47:38 -0700 (PDT),
Post by vinaykabadi
Hello,
I am an software engineer who works for audio development. I have used
Dsound for my capture playback, in the mean while I have found that
the USB camera with mic captures more than specified frequency. I
tried to capture at 8000Hz, 16 bits, mono. But when I get the average
results in 1 minutes.. I found that it is actually capturing around
8100 Hz. The same thing happens for playback too with USB Speakers.
Not only my code it seems that all the audio applications behave in a
same way.
But the sound card devices behaves properly i.e they capture more or
less 8000Hz. I dont understand why Xp behaves like this.
Can sombody help me out to get an work around to avoid this problem.
Regards
Vinay
Does the same thing happen with the built-in sound
chipset? Or with different brands of USB sound?
If it only happens with one particular USB
product, that would make me suspect its own
internal chipset was to blame. If it happens also
with other USB devices and the built-in sound
chipset, then I'd guess it was an XP problem.

I have never found any documentation on when and
where sample rate conversion is performed. I get
the impression that it might be done either by
Windows or by the sound chipset itself.

I do know that there are magic sample rates that
are typically correct, either without SRC or maybe
where the SRC is "perfect". These are usually
integer submultiples of 48000 Hz... so I'd think
your 8000 would be right on.

I'll try to test 8000 on some of my systems later
today and get back to you tomorrow.

Best regards,


Bob Masta

DAQARTA v4.51
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!
Bob Masta
2009-09-17 15:24:28 UTC
Permalink
On Thu, 17 Sep 2009 12:09:21 GMT,
Post by Bob Masta
On Wed, 16 Sep 2009 14:47:38 -0700 (PDT),
Post by vinaykabadi
Hello,
I am an software engineer who works for audio development. I have used
Dsound for my capture playback, in the mean while I have found that
the USB camera with mic captures more than specified frequency. I
tried to capture at 8000Hz, 16 bits, mono. But when I get the average
results in 1 minutes.. I found that it is actually capturing around
8100 Hz. The same thing happens for playback too with USB Speakers.
Not only my code it seems that all the audio applications behave in a
same way.
But the sound card devices behaves properly i.e they capture more or
less 8000Hz. I dont understand why Xp behaves like this.
Can sombody help me out to get an work around to avoid this problem.
Regards
Vinay
Does the same thing happen with the built-in sound
chipset? Or with different brands of USB sound?
If it only happens with one particular USB
product, that would make me suspect its own
internal chipset was to blame. If it happens also
with other USB devices and the built-in sound
chipset, then I'd guess it was an XP problem.
I have never found any documentation on when and
where sample rate conversion is performed. I get
the impression that it might be done either by
Windows or by the sound chipset itself.
I do know that there are magic sample rates that
are typically correct, either without SRC or maybe
where the SRC is "perfect". These are usually
integer submultiples of 48000 Hz... so I'd think
your 8000 would be right on.
I'll try to test 8000 on some of my systems later
today and get back to you tomorrow.
Couldn't wait... this gets curiouser and
curiouser!

Tested on XP with built-in Realtek HD chipset,
plus cheapie "USB Audio" device. Counted ticks
from a multimedia timer set to 1 msec, read wave
sample positions with waveInGetPosition and
waveOutGetPosition. Computed running sample rate,
read it at 120 sec. Tested at 48000, 44100, and
8000 Hz sample rates.

The Realtek was pretty close to specs at all 3
sample rates, whether waveIn-only, waveOut-only,
or full duplex.

The USB Audio was as good as the Realtek for 48000
Hz in all 3 modes.

For 44100 and 8000, it depended upon the mode:

waveOut-only: 44100 was actually 44000, while
8000 was nearly exact.

waveIn-only: 44100 was actually 44083, while 8000
was 8099.

For full-duplex, the results were the same as for
waveIn-only. The really strange part was that if
I then toggled waveIn off and just tested waveOut,
the effective sample rates did not drop back to
their original waveOut readings... I had to close
my app and restart to get back to the originals.

The USB Audio device not sold under any particular
brand name. It is a silver disk with rounded
edges, like a big M&Ms candy, that has 2 big black
buttons and a big white area that flashes red all
the time it is running. Top of it says "USB 5.1
Channel Audio Adapter". No manufacturer shown on
the outside or in the manual. Inside, it uses a
VIA VT1616 6-channel AC97 Codec chip, with a Sonix
controller chip... not sure which is the likely
culprit here.

Best regards,


Bob Masta

DAQARTA v4.51
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!
vinaykabadi
2009-09-17 18:06:59 UTC
Permalink
Post by Bob Masta
On Thu, 17 Sep 2009 12:09:21 GMT,
Post by Bob Masta
On Wed, 16 Sep 2009 14:47:38 -0700 (PDT),
Post by vinaykabadi
Hello,
I am an software engineer who works for audio development. I have used
Dsound for my capture playback, in the mean while I have found that
the USB camera with mic captures more than specified frequency. I
tried to capture at 8000Hz, 16 bits, mono. But when I get the average
results in 1 minutes.. I found that it is actually capturing around
8100 Hz. The same thing happens for playback too with USB Speakers.
Not only my code it seems that all the audio applications behave in a
same way.
But the sound card devices behaves properly i.e they capture more or
less 8000Hz. I dont understand why Xp behaves like this.
Can sombody help me out to get an work around to avoid this problem.
Regards
Vinay
Does the same thing happen with the built-in sound
chipset?  Or with different brands of USB sound?
If it only happens with one particular USB
product, that would make me suspect its own
internal chipset was to blame.  If it happens also
with other USB devices and the built-in sound
chipset, then I'd guess it was an XP problem.  
I have never found any documentation on when and
where sample rate conversion is performed.  I get
the impression that it might be done either by
Windows or by the sound chipset itself.
I do know that there are magic sample rates that
are typically correct, either without SRC or maybe
where the SRC is "perfect".  These are usually
integer submultiples of 48000 Hz... so I'd think
your 8000 would be right on.
I'll try to test 8000 on some of my systems later
today and get back to you tomorrow.
Couldn't wait... this gets curiouser and
curiouser!
Tested on XP with built-in Realtek HD chipset,
plus cheapie "USB Audio" device.  Counted ticks
from a multimedia timer set to 1 msec, read wave
sample positions with waveInGetPosition and
waveOutGetPosition.  Computed running sample rate,
read it at 120 sec.  Tested at 48000, 44100, and
8000 Hz sample rates.
The Realtek was pretty close to specs at all 3
sample rates, whether waveIn-only, waveOut-only,
or full duplex.
The USB Audio was as good as the Realtek for 48000
Hz in all 3 modes.
waveOut-only:  44100 was actually 44000, while
8000 was nearly exact.
waveIn-only:  44100 was actually 44083, while 8000
was 8099.
For full-duplex, the results were the same as for
waveIn-only.  The really strange part was that if
I then toggled waveIn off and just tested waveOut,
the effective sample rates did not drop back to
their original waveOut readings... I had to close
my app and restart to get back to the originals.
The USB Audio device not sold under any particular
brand name.   It is a silver disk with rounded
edges, like a big M&Ms candy, that has 2 big black
buttons and a big white area that flashes red all
the time it is running.  Top of it says "USB 5.1
Channel Audio Adapter".  No manufacturer shown on
the outside or in the manual.  Inside, it uses a
VIA VT1616 6-channel AC97 Codec chip, with a Sonix
controller chip... not sure which is the likely
culprit here.
Best regards,
Bob Masta
              DAQARTA  v4.51
   Data AcQuisition And Real-Time Analysis
             www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
           FREE Signal Generator
        Science with your sound card!- Hide quoted text -
- Show quoted text -
Hi Bob,

Nice to know that you are curious about my problem..

As you said
Post by Bob Masta
waveIn-only: 44100 was actually 44083, while 8000
was 8099
for 8000Hz you got 100 Hz more. It would mean every second 100
samples extra with 16 bits, so 1600 bytes extra in 1 sec. If I capture
for even 5 minutes then

1600 * (60 * 5) = 480000. Thats a huge bulk Bob.

If going to test it out then use only USB device in only Xp systems.
The problems lies there. You can use any good brands, Microsoft
lifecam, logitech pro 9000, etc all have this problem. You can test
Playback with USB spekears or headset.

Thanks
Vinay
vinaykabadi
2009-09-21 18:01:04 UTC
Permalink
Post by vinaykabadi
Post by Bob Masta
On Thu, 17 Sep 2009 12:09:21 GMT,
Post by Bob Masta
On Wed, 16 Sep 2009 14:47:38 -0700 (PDT),
Post by vinaykabadi
Hello,
I am an software engineer who works for audio development. I have used
Dsound for my capture playback, in the mean while I have found that
the USB camera with mic captures more than specified frequency. I
tried to capture at 8000Hz, 16 bits, mono. But when I get the average
results in 1 minutes.. I found that it is actually capturing around
8100 Hz. The same thing happens for playback too with USB Speakers.
Not only my code it seems that all the audio applications behave in a
same way.
But the sound card devices behaves properly i.e they capture more or
less 8000Hz. I dont understand why Xp behaves like this.
Can sombody help me out to get an work around to avoid this problem.
Regards
Vinay
Does the same thing happen with the built-in sound
chipset?  Or with different brands of USB sound?
If it only happens with one particular USB
product, that would make me suspect its own
internal chipset was to blame.  If it happens also
with other USB devices and the built-in sound
chipset, then I'd guess it was an XP problem.  
I have never found any documentation on when and
where sample rate conversion is performed.  I get
the impression that it might be done either by
Windows or by the sound chipset itself.
I do know that there are magic sample rates that
are typically correct, either without SRC or maybe
where the SRC is "perfect".  These are usually
integer submultiples of 48000 Hz... so I'd think
your 8000 would be right on.
I'll try to test 8000 on some of my systems later
today and get back to you tomorrow.
Couldn't wait... this gets curiouser and
curiouser!
Tested on XP with built-in Realtek HD chipset,
plus cheapie "USB Audio" device.  Counted ticks
from a multimedia timer set to 1 msec, read wave
sample positions with waveInGetPosition and
waveOutGetPosition.  Computed running sample rate,
read it at 120 sec.  Tested at 48000, 44100, and
8000 Hz sample rates.
The Realtek was pretty close to specs at all 3
sample rates, whether waveIn-only, waveOut-only,
or full duplex.
The USB Audio was as good as the Realtek for 48000
Hz in all 3 modes.
waveOut-only:  44100 was actually 44000, while
8000 was nearly exact.
waveIn-only:  44100 was actually 44083, while 8000
was 8099.
For full-duplex, the results were the same as for
waveIn-only.  The really strange part was that if
I then toggled waveIn off and just tested waveOut,
the effective sample rates did not drop back to
their original waveOut readings... I had to close
my app and restart to get back to the originals.
The USB Audio device not sold under any particular
brand name.   It is a silver disk with rounded
edges, like a big M&Ms candy, that has 2 big black
buttons and a big white area that flashes red all
the time it is running.  Top of it says "USB 5.1
Channel Audio Adapter".  No manufacturer shown on
the outside or in the manual.  Inside, it uses a
VIA VT1616 6-channel AC97 Codec chip, with a Sonix
controller chip... not sure which is the likely
culprit here.
Best regards,
Bob Masta
              DAQARTA  v4.51
   Data AcQuisition And Real-Time Analysis
             www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
           FREE Signal Generator
        Science with your sound card!- Hide quoted text -
- Show quoted text -
Hi Bob,
Nice to know that you are curious about my problem..
As you said
Post by Bob Masta
waveIn-only:  44100 was actually 44083, while 8000
was 8099
for 8000Hz you got 100 Hz more. It would mean every second  100
samples extra with 16 bits, so 1600 bytes extra in 1 sec. If I capture
for even 5 minutes then
1600 * (60 * 5) = 480000. Thats a huge bulk Bob.
If going to test it out then use only USB device in only Xp systems.
The problems lies there. You can use any good brands, Microsoft
lifecam, logitech pro 9000, etc all have this problem. You can test
Playback with USB spekears or headset.
Thanks
Vinay- Hide quoted text -
- Show quoted text -
Hi Bob,

I Guess you are busy... but did you find anything about the USB Audio
in Xp. If yes then kindly let me know, I am waiting only for your
reply. Based on your reply I will talk to microsoft in this concern.

Regards
Vinay
Bob Masta
2009-09-22 12:30:23 UTC
Permalink
On Mon, 21 Sep 2009 11:01:04 -0700 (PDT),
Post by vinaykabadi
Post by vinaykabadi
Post by Bob Masta
On Thu, 17 Sep 2009 12:09:21 GMT,
Post by Bob Masta
On Wed, 16 Sep 2009 14:47:38 -0700 (PDT),
Post by vinaykabadi
Hello,
I am an software engineer who works for audio development. I have use=
d
Post by vinaykabadi
Post by Bob Masta
Post by Bob Masta
Post by vinaykabadi
Dsound for my capture playback, in the mean while I have found that
the USB camera with mic captures more than specified frequency. I
tried to capture at 8000Hz, 16 bits, mono. But when I get the average
results in 1 minutes.. I found that it is actually capturing around
8100 Hz. The same thing happens for playback too with USB Speakers.
Not only my code it seems that all the audio applications behave in a
same way.
But the sound card devices behaves properly i.e they capture more or
less 8000Hz. I dont understand why Xp behaves like this.
Can sombody help me out to get an work around to avoid this problem.
Regards
Vinay
Does the same thing happen with the built-in sound
chipset? =A0Or with different brands of USB sound?
If it only happens with one particular USB
product, that would make me suspect its own
internal chipset was to blame. =A0If it happens also
with other USB devices and the built-in sound
chipset, then I'd guess it was an XP problem. =A0
I have never found any documentation on when and
where sample rate conversion is performed. =A0I get
the impression that it might be done either by
Windows or by the sound chipset itself.
I do know that there are magic sample rates that
are typically correct, either without SRC or maybe
where the SRC is "perfect". =A0These are usually
integer submultiples of 48000 Hz... so I'd think
your 8000 would be right on.
I'll try to test 8000 on some of my systems later
today and get back to you tomorrow.
Couldn't wait... this gets curiouser and
curiouser!
Tested on XP with built-in Realtek HD chipset,
plus cheapie "USB Audio" device. =A0Counted ticks
from a multimedia timer set to 1 msec, read wave
sample positions with waveInGetPosition and
waveOutGetPosition. =A0Computed running sample rate,
read it at 120 sec. =A0Tested at 48000, 44100, and
8000 Hz sample rates.
The Realtek was pretty close to specs at all 3
sample rates, whether waveIn-only, waveOut-only,
or full duplex.
The USB Audio was as good as the Realtek for 48000
Hz in all 3 modes.
waveOut-only: =A044100 was actually 44000, while
8000 was nearly exact.
waveIn-only: =A044100 was actually 44083, while 8000
was 8099.
For full-duplex, the results were the same as for
waveIn-only. =A0The really strange part was that if
I then toggled waveIn off and just tested waveOut,
the effective sample rates did not drop back to
their original waveOut readings... I had to close
my app and restart to get back to the originals.
The USB Audio device not sold under any particular
brand name. =A0 It is a silver disk with rounded
edges, like a big M&Ms candy, that has 2 big black
buttons and a big white area that flashes red all
the time it is running. =A0Top of it says "USB 5.1
Channel Audio Adapter". =A0No manufacturer shown on
the outside or in the manual. =A0Inside, it uses a
VIA VT1616 6-channel AC97 Codec chip, with a Sonix
controller chip... not sure which is the likely
culprit here.
Best regards,
Bob Masta
=A0 =A0 =A0 =A0 =A0 =A0 =A0 DAQARTA =A0v4.51
=A0 =A0Data AcQuisition And Real-Time Analysis
=A0 =A0 =A0 =A0 =A0 =A0 =A0www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
=A0 =A0 =A0 =A0 =A0 =A0FREE Signal Generator
=A0 =A0 =A0 =A0 Science with your sound card!- Hide quoted text -
- Show quoted text -
Hi Bob,
Nice to know that you are curious about my problem..
As you said
Post by Bob Masta
waveIn-only: =A044100 was actually 44083, while 8000
was 8099
for 8000Hz you got 100 Hz more. It would mean every second =A0100
samples extra with 16 bits, so 1600 bytes extra in 1 sec. If I capture
for even 5 minutes then
1600 * (60 * 5) =3D 480000. Thats a huge bulk Bob.
If going to test it out then use only USB device in only Xp systems.
The problems lies there. You can use any good brands, Microsoft
lifecam, logitech pro 9000, etc all have this problem. You can test
Playback with USB spekears or headset.
Thanks
Vinay- Hide quoted text -
- Show quoted text -
Hi Bob,
I Guess you are busy... but did you find anything about the USB Audio
in Xp. If yes then kindly let me know, I am waiting only for your
reply. Based on your reply I will talk to microsoft in this concern.
I'm not sure what else to test. I only have the
one USB Audio device available. If this behavior
happens in different brands of USB device as you
say, then the possibilities would seem to be
either that they all use the same VIA VT1616
6-channel AC97 Codec chip (which might not be too
surprising), or that Windows itself imposes a
special USB driver between the device and the
normal wave API operation.

At this point I don't know how to tell between
these two possibilities. If it really is Windows
causing the problem, then what can we conclude
about the interaction with the USB device? Is the
USB actually sampling at the specified 8000 Hz and
Windows is resampling for mysterious reasons? Or
is Windows intercepting commands to set the USB
sample rate, and replacing them with wrong values?
Neither of these seem likely, so before I jumped
on Microsoft I'd try looking at the innards of
some of these other devices to see if they all use
the same chipset.

I suppose one thing that could be done is to open
up a device and probe the codec. I am pretty sure
the VIA VT1616 data sheet is available on-line; if
so, see if there is a sample rate clock you can
hang a frequency counter onto. If it is actually
8000, then you would know that Windows must be
resampling for its own mysterious reasons. On the
other hand, if it is 8100 you still wouldn't know
if the chip did that in response to a request for
8000, or if Windows changed the request.

Do you get the same behavior with Vista? If not,
you'd know for sure that the problem was in XP.
Of course, if this is a Windows problem then it
might very well have been carried over to Vista as
well.

Sorry I don't have any definite answers to offer!


Bob Masta

DAQARTA v4.51
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!
vinaykabadi
2009-09-22 18:42:18 UTC
Permalink
Post by Bob Masta
On Mon, 21 Sep 2009 11:01:04 -0700 (PDT),
Post by vinaykabadi
Post by vinaykabadi
Post by Bob Masta
On Thu, 17 Sep 2009 12:09:21 GMT,
Post by Bob Masta
On Wed, 16 Sep 2009 14:47:38 -0700 (PDT),
Post by vinaykabadi
Hello,
I am an software engineer who works for audio development. I have use=
d
Post by vinaykabadi
Post by Bob Masta
Post by Bob Masta
Post by vinaykabadi
Dsound for my capture playback, in the mean while I have found that
the USB camera with mic captures more than specified frequency. I
tried to capture at 8000Hz, 16 bits, mono. But when I get the average
results in 1 minutes.. I found that it is actually capturing around
8100 Hz. The same thing happens for playback too with USB Speakers.
Not only my code it seems that all the audio applications behave in a
same way.
But the sound card devices behaves properly i.e they capture more or
less 8000Hz. I dont understand why Xp behaves like this.
Can sombody help me out to get an work around to avoid this problem.
Regards
Vinay
Does the same thing happen with the built-in sound
chipset? =A0Or with different brands of USB sound?
If it only happens with one particular USB
product, that would make me suspect its own
internal chipset was to blame. =A0If it happens also
with other USB devices and the built-in sound
chipset, then I'd guess it was an XP problem. =A0
I have never found any documentation on when and
where sample rate conversion is performed. =A0I get
the impression that it might be done either by
Windows or by the sound chipset itself.
I do know that there are magic sample rates that
are typically correct, either without SRC or maybe
where the SRC is "perfect". =A0These are usually
integer submultiples of 48000 Hz... so I'd think
your 8000 would be right on.
I'll try to test 8000 on some of my systems later
today and get back to you tomorrow.
Couldn't wait... this gets curiouser and
curiouser!
Tested on XP with built-in Realtek HD chipset,
plus cheapie "USB Audio" device. =A0Counted ticks
from a multimedia timer set to 1 msec, read wave
sample positions with waveInGetPosition and
waveOutGetPosition. =A0Computed running sample rate,
read it at 120 sec. =A0Tested at 48000, 44100, and
8000 Hz sample rates.
The Realtek was pretty close to specs at all 3
sample rates, whether waveIn-only, waveOut-only,
or full duplex.
The USB Audio was as good as the Realtek for 48000
Hz in all 3 modes.
waveOut-only: =A044100 was actually 44000, while
8000 was nearly exact.
waveIn-only: =A044100 was actually 44083, while 8000
was 8099.
For full-duplex, the results were the same as for
waveIn-only. =A0The really strange part was that if
I then toggled waveIn off and just tested waveOut,
the effective sample rates did not drop back to
their original waveOut readings... I had to close
my app and restart to get back to the originals.
The USB Audio device not sold under any particular
brand name. =A0 It is a silver disk with rounded
edges, like a big M&Ms candy, that has 2 big black
buttons and a big white area that flashes red all
the time it is running. =A0Top of it says "USB 5.1
Channel Audio Adapter". =A0No manufacturer shown on
the outside or in the manual. =A0Inside, it uses a
VIA VT1616 6-channel AC97 Codec chip, with a Sonix
controller chip... not sure which is the likely
culprit here.
Best regards,
Bob Masta
=A0 =A0 =A0 =A0 =A0 =A0 =A0 DAQARTA =A0v4.51
=A0 =A0Data AcQuisition And Real-Time Analysis
=A0 =A0 =A0 =A0 =A0 =A0 =A0www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
=A0 =A0 =A0 =A0 =A0 =A0FREE Signal Generator
=A0 =A0 =A0 =A0 Science with your sound card!- Hide quoted text -
- Show quoted text -
Hi Bob,
Nice to know that you are curious about my problem..
As you said
Post by Bob Masta
waveIn-only: =A044100 was actually 44083, while 8000
was 8099
for 8000Hz you got 100 Hz more. It would mean every second =A0100
samples extra with 16 bits, so 1600 bytes extra in 1 sec. If I capture
for even 5 minutes then
1600 * (60 * 5) =3D 480000. Thats a huge bulk Bob.
If going to test it out then use only USB device in only Xp systems.
The problems lies there. You can use any good brands, Microsoft
lifecam, logitech pro 9000, etc all have this problem. You can test
Playback with USB spekears or headset.
Thanks
Vinay- Hide quoted text -
- Show quoted text -
Hi Bob,
I Guess you are busy... but did you find anything about the USB Audio
in Xp. If yes then kindly let me know, I am waiting only for your
reply. Based on your reply I will talk to microsoft in this concern.
I'm not sure what else to test.  I only have the
one USB Audio device available.  If this behavior
happens in different brands of USB device as you
say, then the possibilities would seem to be
either that they all use the same VIA VT1616
6-channel AC97 Codec chip (which might not be too
surprising), or that Windows itself imposes a
special USB driver between the device and the
normal wave API operation.  
At this point I don't know how to tell between
these two possibilities.  If it really is Windows
causing the problem, then what can we conclude
about the interaction with the USB device?  Is the
USB actually sampling at the specified 8000 Hz and
Windows is resampling for mysterious reasons?  Or
is Windows intercepting commands to set the USB
sample rate, and replacing them with wrong values?
Neither of these seem likely, so before I jumped
on Microsoft I'd try looking at the innards of
some of these other devices to see if they all use
the same chipset.
I suppose one thing that could be done is to open
up a device and probe the codec.  I am pretty sure
the VIA VT1616 data sheet is available on-line; if
so, see if there is a sample rate clock you can
hang a frequency counter onto.  If it is actually
8000, then you would know that Windows must be
resampling for its own mysterious reasons.  On the
other hand, if it is 8100 you still wouldn't know
if the chip did that in response to a request for
8000, or if Windows changed the request.
Do you get the same behavior with Vista?  If not,
you'd know for sure that the problem was in XP.
Of course, if this is a Windows problem then it
might very well have been carried over to Vista as
well.
Sorry I don't have any definite answers to offer!
Bob Masta
              DAQARTA  v4.51
   Data AcQuisition And Real-Time Analysis
             www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
           FREE Signal Generator
        Science with your sound card!- Hide quoted text -
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Thanks BOB

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